l66 A MANUAL OF FORESTRY 



B. ESTIMATING TIMBER ON LARGE WOOD LOTS. 



On large wood lots, as those over one hundred acres in extent, 

 very likely it would be impracticable to measure all the trees. 

 A system somewhat less accurate can be applied in such cases 

 depending upon two operations carried on together, as follows: 



1. Count all the trees on the lot. 



2, Measure all the trees on certain plots. 



Two men by walking through a forest on a compass course can 

 very rapidly count the trees on a strip four rods wide. Those on 

 the outside should be marked so as to avoid confusion when 

 returning on the parallel strip. At regular distances, as every 

 two hundred paces, a plot is laid off and all the trees on this plot 

 measured as described under A . Circular plots are conveniently 

 laid off by pacing from the center the distance of the required 

 radius in different directions. A circle with a radius of 59 feet 

 contains a quarter acre; with a radius of 85 feet, a half acre. 

 After all the trees on the wood lot have been counted in this way, 

 and the trees on several sample plots have been measured, the 

 volumes of the various sample plots are worked up by one of the 

 methods described under A. The total volume of the lot is 

 obtained by ratio: 



X:V:: N: n 

 in which 



X = total volume of 'the wood lot. 



V = volume of the sample plots. 



N = total number of trees on the wood lot. 



n = number of trees on the sample plots. 



C. ESTIMATING TIMBER ON LARGE FOREST TRACTS. 



The methods described above rely upon a census of the total 

 number of trees on the wood lot. In the case of large timber 

 tracts such an enumeration is impossible, and some method must 

 be employed based on an accurate estimate of certain parts of the 

 tract and a knowledge of what proportion these areas form of the 



